One of the greatest concerns in the design of US Army combat vehicle is crew protection, and one of the greatest hazards is fire in the vehicle's crew compartment when enemy rounds damage the vehicle. Such a fire is especially dangerous because combat vehicle crew compartments are confined spaces and any fire therein is thus likely to cause injury. In addition, ammunition magazines in the vehicle make any vehicle fire a potential disaster. Consequently, fire extinguishing systems for combat vehicles are designed to act automatically and instantaneously to flood the entire interior of the vehicle once sensors detect a fire.
Traditionally, fire extinguishing systems for combat vehicle use metal bottles containing a highly volatile extinguishant such as Halon 1211 or Halon 1301. The bottle is normally pressurized by compressed nitrogen gas, so that opening a valve in the bottle allows the nitrgen's pressure to expel the extinguishant. However, the US Army is presently attempting to find a replacement for Halon extinguishants because of their adverse environmental impacts.
I have invented a fire extinguishing system that can use either Halon extinguishants or other extinguishants so that little or no modification to the system is required as the Army phases out Halon extinguishants. In addition my system does not require a highly volatile extinguishant to be stored under the same high pressures currently used, which reduces safety concerns. In one embodiment of my invention, no gas or fluid is required to be stored under high pressure so that safety concerns are further reduced and the need to periodically check the fire extinguishing system for proper pressure is eliminated.
My system incorporates a shock tube construction. The system has two shock tube sections joined by flanges and sealed from one another by a diaphragm. The first shock tube section contains either fluid under high pressure or a gas generator, and the second shock tube section contains a volatile, low-boiling-point extinguishant. When the system actuates, the diaphragm is ruptured either by a squib or by a sudden pressure increase in the first shock tube section. The pressure in the first shock tube section propagates a shock wave through the extinguishant in the second shock tube section. The shock wave imparts such enthalpy to the extinguishant that the extinguishant becomes highly pressurized and ruptures a second diaphragm. The second diaphragm is at the opposite end of the second shock tube section from the first diaphragm and is disposed between the second shock tube section and a conduit. After the second diaphragm ruptures, the extinguishant travels along the conduit to a nozzle or spray head from which the extinguishant is dispersed into the vehicle compartment.